The present invention relates to an electrically insulating thermal joint which provides electrical insulation while transferring heat across the joint with a minimum temperature difference across the joint.
In a superconducting magnet which operates without consumable cryogens, helium cooling is not available to reduce conduction heat transfer to the superconducting magnet from the ambient environment and to dissipate the resistance heating of the metallic resistive conductors. A magnet cryostat equipped with a recondensor or cryocooler permits no loss of helium since they operate as a closed loop system. Thermal losses of conventional permanently attached metallic leads usually handled by escaping helium vapor cannot be tolerated for long in a system having a recondensor, a cryocooler and no consumable cryogens. All heat carried to the magnet in the cryostat by radiation and conduction must be removed by the cryocooler so that the heat does not raise the magnet temperature above the transition temperature of the superconductor.
In a magnet configuration having superconductor windings and resistive joints, permanently connected leads can be used to maintain current at a constant value. Permanently connected leads, however, carry heat into the magnet due to heat conduction from higher temperatures and heat generated due to the resistance of the leads.
The cooling stations of the cryocooler can be used to remove heat from the leads but the leads have to be electrically isolated from the cryocooler and one another while still having a sufficiently high thermal conductivity so that heat transferred down the leads can be intercepted before it reaches the magnet.
It is an object of the present invention to provide a joint between a lead and a cryocooler heat station which will electrically insulate the leads from the cryocooler heat station while transferring heat from the leads to the interface with a minimal temperature difference across the joint.